Teachers must have accurate, up-to-date knowledge about biodiversity in order to help prepare world citizens to cope with the problems of decreasing variability on our planet. The objectives of this study were to: (1) develop a reliable, valid test of teacher knowledge about biodiversity; (2) administer this test to K-12 teachers to determine their current knowledge about biodiversity; and (3) determine how selected teacher demographic variables relate to test scores. The theoretical framework for the development of this test was based on the classification of knowledge about biodiversity into three levels of variability: (1) ecosystem level; (2) species level; and (3) genetic/molecular level. Each of 44 questions developed for a true/false biodiversity test represented knowledge about one of these three levels. Based on evaluation of the test by ecologists and logical analysis, the test was found to be valid. This test was administered to 64 K-12 teachers enrolled in an environmental education course. The average score on the test was about 50%. Teacher knowledge about biodiversity did not differ much for each of the three biodiversity levels. The number of environmental/environmental education courses taken by teachers was positively related to teacher knowledge about biodiversity. Appendix contains a copy of the test. Contains 12 references. (Author/PVD)